Sun, Ocean, Nuclear Bombs, and Fossil Fuels: Radiocarbon Variations and Implications for High-Resolution Dating

Radiocarbon, or 14 C, is a radiometric dating method ideally suited for providing a chronological framework in archaeology and geosciences for timescales spanning the last 50,000 years. 14 C is easily detectable in most common natural organic materials and has a half-life (5,730±40 years) relevant to these timescales. 14 C produced from large-scale detonations of nuclear bombs between the 1950s and the early 1960s can be used for dating modern organic materials formed after the 1950s. Often these studies demand high-resolution chronology to resolve ages within a few decades to less than a few years. Despite developments in modern, high-precision 14 C analytical methods, the applicability of 14 C in high-resolution chronology is limited by short-term variations in atmospheric 14 C in the past. This article reviews the roles of the principal natural drivers (e.g., solar magnetic activity and ocean circulation) and the anthropogenic perturbations (e.g., fossil fuel CO 2 and 14 C from nuclear and thermonuclear bombs) that are responsible for short-term 14 C variations in the environment. Methods and challenges of high-resolution 14 C dating are discussed.